This invention relates to the field of ground fault circuit interrupters having a two pole breaking mechanism, one pole for the hot or electrified conductor and one for the neutral conductor. A problem arises with such two pole breakers if the hot contacts inadvertently make first and the neutral contacts remain separated. The circuit downstream from the ground fault circuit interrupter, or the device which it is supposed to protect, will be hot, but the ground fault interrupting mechanism will not be powered as long as the neutral contacts are separated. The trip coil cannot operate to trip the interrupting mechanism, and whatever indication means are provided will indicate a set or operative condition. An inspection of the indicator would lead one to believe the ground fault mechanism was operative and the circuit protected when in fact this would not be the case.
Previous attempts to solve this problem have included a separate switch to energize the ground fault circuit interrupter before the main breakers close and to de-energize the interrupter after the main circuit breaker contacts open on occurrence of a ground fault. Another approach to the problem made use of an overcenter compression device associated in an appropriate manner with the main circuit breaker contacts, whereby the contacts are urged to a fully open or a fully closed position but could not be held in between. The present invention dispenses with the need for either a separate switch, compression member or other additional component. Instead, it provides sequential contact opening and closing means which opens or breaks the hot contacts first and the neutral thereafter, and which conversely closes or makes the neutral contacts first and the hot contacts only after the neutral contacts have closed. The structure which incorporates such means in accordance with this invention includes a contact carrier having a transversely rockable contact arm, one end of which carrying the hot or electrified contact is movable a greater relative distance then the opposite end carrying the neutral contact when the contact carrier is moved both in a contact closing direction and a contact opening direction.
Means to provide greater relative movement for the hot contact side of the contact arm may be incorporated in the movable contacts or carrier, or alternatively in the corresponding stationary contacts or mountings. The movable contact carrier may have a transversely canted or inclined groove underneath to receive the main spring cross bar, the groove being deeper toward the hot contact side of the contact arm to enable that side to move relatively greater distances than the opposite neutral contact side.
One or both of the neutral contacts may be longer in elevation (or mounted closer together) so the gap between them when open is shorter than the gap between the hot contacts. The hot contact side of the contact arm will therefore have to travel relatively greater distances to open and close than the opposite neutral contact side. When the neutral contacts close across the relatively shorter gap, the hot contacts are still separated. The main spring biased against the underside of the contact carrier rocks the still separated hot contact side of the contact arm in the closing direction causing the contact arm and carrier to cant somewhat until the hot contacts are also closed.